This invention relates to a solenoid control apparatus which is mounted e.g. in a vehicle brake hydraulic pressure control system.
Such a solenoid control apparatus is disclosed in JP Patent Publication 2002-368452A which is in the form of an electronic control apparatus for a vehicle brake hydraulic pressure control system. This electronic control apparatus includes a circuit board mounted in a resin housing and carrying an electronic control unit (ECU) thereon for driving solenoid valves to selectively connect and disconnect hydraulic lines and adjust the degree of opening of the hydraulic lines by controlling valve portions of the solenoid valves.
The housing includes a circuit board mounting portion in which the circuit board is mounted, a solenoid mounting portion in which the solenoid coils of the solenoid valves are mounted, and an overhanging connector portion extending in the direction of the top surface of the circuit board and integrally connected to one side of the solenoid mounting portion. The interior of the solenoid mounting portion is separated from the interior of the circuit board mounting portion by a partition wall of the housing. The circuit board is a rigid circuit board.
The connector portion is connected to the solenoid mounting portion through a connecting portion (bridge) which is located on an extension of the partition wall and an extension of an end wall of the connector portion. The solenoids have terminals extending through the partition plate and the circuit board and soldered to the electrical circuit on the circuit board. The connector portion has terminals for connection to the power source and a communication circuit that extend through the end wall of the connector portion and the circuit board and soldered to the electrical circuit on the circuit board.
The overhanging connector portion of the resin housing of such a solenoid control apparatus tends to be deformed (warped) by heat from the environment and heat from the electrical circuit of the circuit board.
In order to cope with such thermal deformation of the connector portion, JP Patent Publication 2002-368452A proposes to allow movement of the circuit board following deformation of the connector portion, thereby reducing stress on the soldered portions on the circuit board.
But this arrangement is unable to reduce stress due to a difference in thermal expansion between the circuit board and the resin housing. Such stress could result in cracks in the soldered portions, which could in turn cause poor electrical connection.
If, instead of soldering the terminals, the terminals are press-fitted into through holes formed in the circuit board and fixed to the electrical circuit on the circuit board, the stress due to a difference in thermal expansion could cause separation of the terminals from the holes.